The present invention is directed to a patient operated instrument and method for testing and recording a biological condition of the patient, and more specifically to a system which measures the forced peak expiratory flow of air expelled by the patient when blowing into a measuring tube, as well as other respiratory functions.
Devices of this type are known as peak flow meters, which measure the peak expiratory flow rate (PEFR) that occurs during the first few hundred milliliters of volume expired, when a maximum exhalation is carried out forcibly from total lung capacity. Other devices are known which measure forced expiratory volume in the first second (FEV. 1) and forced vital capacity (FVC). These procedures are patient dependent with regard to effort and volume.
According to the National Institute of Health National Asthma Education program's statement on the technical standards for peak flow meters, released in February 1991, if properly utilized, measurement of PEFR serves as a valuable adjunct to patient care.
Numerous products exist that have the capability to measure PEFR, FEV. 1 and FVC. However, most peak flow meters in particular are mechanical devices that lack calibration capability and all require the patient to manually record the data derived from the peak flow test. A major disadvantage of these prior art devices is the lack of patient compliance with diligent manual recording, as well as the lack of accurate and objective recording of test results.
Moreover, while most peak flow meters are accurate in the mid-range, errors in the high or low ranges are not uncommon. Additionally, temperature and humidity are not compensated for in these units and the wearing out of mechanical parts causes significant errors in some if not all devices over the course of time.
Another problem that exists with regard to prior art peak flow meters is that the patient is expected to remember to take tests at specific times during the course of each day, take the prescribed medications after each test, evaluate the performance of the medication by repeating the test several minutes later and then record the results. It is no wonder that the problem of non-compliance is particularly prevalent for devices of this type.